1. 1 Internet Protocol Version 6 (IPv6) What the caterpillar calls the end of the world, nature calls a butterfly. - Anonymous

2. 2 Objectives Describe the advantages of IPv6 over IPv4 Explain the format and types of IPv6 addresses Explain the IPv6 packet format Explain the strategies for transitioning from IPv4 to IPv6

3. 3 Larger address space (128 bits long addresses) Better header format (40-byte fixed-size base header containing essential fields; optional extension headers with other fields for added functionality) New options for additional functionality Allows extension of the protocol Added security with encryption and authentication options Advantages of IPv6 over IPv4

4. 4 Expressed using hexadecimal notation (0-F), with eight 16-bit portions separated by colons (:) Contiguous zeros may be abbreviated IPv6 Addresses

5. 5 Abbreviated IPv6 Addresses

6. 6 Categories of Addresses Unicast address - assigned to an individual host Anycast address - assigned to a group of hosts. A packet sent to an anycast address will be delivered to one of the members of the host group. Multicast address - A packet sent to a multicast address will be delivered to all the members of the group

7. 7 Address Structure and Assignment Type Prefix - Variable length prefix defines the purpose of the address Address Type Binary Prefix Unspecified 000…000 (128 bits) Loopback 000…001 (128 bits) Multicast11111111 Link local unicast1111111010 Global unicast(Everything else)

8. 8 Global Unicast Addresses (RFC 4291) Assigned to individual hosts. The general format is: “Global Routing Prefix” is a (typically hierarchically structured) value assigned to a site (a cluster of subnet/links) “Interface ID” is used to identify the interfaces on a link. They should be unique within a subnet prefix. Global Routing PrefixSubnet IDInterface ID n bitsm bits128-n-m bits

9. 9 Special Addresses Unspecified address - entire address consists of all zeroes (abbreviated as ::). Hosts that do not yet know their own address may use this at start-up, in an inquiry to find its address. Loopback address - consists of all zeroes except for the least significant bit (i.e., rightmost bit), which is set to 1. Can be abbreviated as ::1

10. 10 IPv6 Addresses with embedded IPv4 Addresses To ease the introduction of IPv6 and allow both versions of IP to coexist, the IETF defined two types of IPv6 addresses that contain IPv4 addresses within them These are: IPv4-mapped IPv6 addresses and IPv4- compatible IPv6 addresses The first 80 bits of both types are set to all zeroes The last 32 bits of each contain the IPv4 address

11. 11 Figure 27.11 IPv4 Mapped IPv6 addresses This address type is used to represent the addresses of IPv4 nodes as IPv6 addresses

12. 12 Figure 27.10 IPv4 Compatible IPv6 addresses This type is now deprecated because the current IPv6 transition mechanisms no longer use these addresses. New or updated implementations are not required to support this address type.

13. 13 Figure 27.15 IPv6 datagram Base Header is mandatory Payload consists of one or more optional extension headers and data from the upper layer

14. 14 Figure 27.16 Format of an IPv6 datagram

15. 15 IPv6 Base Header Fields Version: Set to binary 0110 (decimal 6) Priority: Priority of each packet with respect to other packets from the same source. If a router has to drop a packet, packets with lower priority are dropped first. Flow Label: A sequence of packets sent from a specific source to a specific destination is called a flow of packets. A router can identify a flow uniquely using Flow Label, and provide any special handling if needed.

16. 16 IPv6 Base Header Fields Payload Length: Length of the datagram excluding the base header Hop Limit: Serves the same purpose as TTL in IPv4 Source & Destination Addresses: IPv6 Addresses of the originating host and the destination host Next Header: Defines the header that follows the base header. The next header is either an optional header or header of a protocol such as: TCP, UDP, ICMP, etc.

17. 17 Table 27.2 Next header codes

18. 18 Figure 27.17 Extension header format

19. 19 Figure 27.18 Extension header types

20. 20 Figure 27.26 Fragmentation Extension Header Unlike IPv4, fragmentation in IPv6 is performed only by source nodes, not by routers along a packet's delivery path A source must use a Path MTU Discovery technique to find the smallest MTU supported by any link on the path

21. 21 Transition from IPv4 to IPv6 The designers of IPv6 anticipated co-existence of IPv4 and IPv6 probably for many years and had defined transition strategies to allow co-existence and gradual migration to IPv6 Figure 27.48 Three transition strategies

22. 22 Dual Stack Approach Dual stack hosts & routers understand both IPv4 and IPv6 To determine which version to use when sending a packet to a destination, the source host queries the DNS. If the DNS returns an IPv4 address, source host sends an IPv4 packet. If the DNS returns an IPv6 address, source host sends an IPv6 packet.

23. 23 Tunneling through an IPv4 region Tunneling can be used when two IPv6 hosts need to communicate through an IPv4 network The routers on both ends of the tunnels must be dual stack routers, capable of understanding both IPv4 and IPv6 IPv6 packet is encapsulated in an IPv4 packet when it enters the IPv4 region. When the interim IPv4 packet reaches the distant IPv6 dual stack router (i.e., when the IPv4 packet leaves the IPv4 region), that router strips off the IPv4 header and routes the packet on its local IPv6 network normally

24. 24 Header Translation Used when the majority of the Internet has moved to IPv6, but some systems still use IPv4. The sender wants to use IPv6, but the receiver does not understand IPv6. In this case, IPv6 header should be converted to an IPv4 header Header translation uses the IPv4-mapped IPv6 addresses to translate an IPv6 address to an IPv4 address. Translation rules specify how to handle the differences between the IPv6 & IPv4 header fields. (E.g: IPv6 Flow Label is ignored in the translation, as there is no corresponding field in the IPv4 header).

25. 25 References RFC 2460, “Internet Protocol, Version 6 (IPv6) Specification”, Dec. 1998 RFC 4291, “IP Version 6 Addressing Architecture”, Feb. 2006 RFC 4038, “Application Aspects of IPv6 Transition”, March 2005